Lower cambrian metallogenesis of south China: Interplay between diverse basinal hydrothermal fluids and marine chemistry

Abstract

The lowermost Cambrian metalliferous black shales of southern China represent a unique metallogenic province. The shales host a wide range of world-class synsedimentary metal deposit types. The diverse metal assemblages in these deposits are best explained by venting of multiple hydrothermal fluids including reduced H2S-rich brines, petroleum, and oxidized brines into the basin. Coinciden formation of shales that are extraordinarity rich in organic carbon and metals suggest a rapid increase in bioproductivity and anoxic/dysoxic conditions during ore formation. We propose that basinal fluids were the source of bioliming nutrients that caused eutrophication and basin-wide anoxia. The dramatic geologic and geochemical changes in this basin demonstrate the possible impacts of hydrothermal systems on the generation and sequestration of organic matter, formation of black metalliferous shales, and chemical changes of seawater.